1. Field of the Invention
This invention relates to the improvements in broadcast antennas and more particularly to a multiple antenna mounting configuration having reduced structural requirements.
2. Description of Related Art
Antennas are used in, for example, television broadcast systems. To provide an antenna with maximized omni-directional coverage, the antenna is typically mounted at the top of a tower or other tall mounting structure. To avoid azimuth pattern degradation due to scattering effects of near metal objects, for example the structural supports and or other antennas, it is preferred that only a single antenna be mounted at a top of each tower or other support structure. However, growth of television, especially digital television, has increased the need for multiple antenna mountings with multiple radiation pattern arrangements on top of antenna towers or other antenna mounting structures.
Prior multiple tower top antenna mounting solutions include offset stack and or in line stacked antenna configurations. Offset stack antenna configurations generally have degraded azimuth patterns due to the proximity of the other, nearby, structure(s) and antenna feed lines. Stacked antennas add a significant structural requirement to the tower and or the individual antennas. An overturning moment that the stacked antenna exerts upon the tower at the antenna mounting point increases as the length of the antennas is increased, in a stacked configuration (each of the antenna structures being, for example 40 to 80 feet in length) the required structural reinforcement of both the antennas and the tower may make the overall cost prohibitive.
Another prior solution is integration of a lower antenna as a portion of the support structure for another antenna mounted above. In this solution, described in detail in U.S. Pat. No. 6,492,959, issued Dec. 10, 2002 to Heatherwick et al and hereby incorporated by reference in the entirety, because the antenna is part of the support structure for the above mounted antenna, the lower antenna cannot demand the same tower real estate lease rates as an antenna located at the highest point of the tower. Also, where more than two antennas are desired, the spacing of the third antenna either on top of the support structure or as another portion of the support structure, below the top mounted antenna(s), from the other antenna(s) is limited by the tower cross section dimensions.
Competition within the broadcast antenna industry has focused attention on signal quality, azimuth patterns, equipment and personnel costs, as well as time requirements for installation and maintenance of broadcast antenna systems.
Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art.